As a monolith which is an inorganic porous body having a three-dimensional continuous network structure, there is a titania monolith formed of a titanium oxide (titania) manufactured by using a titanium compound such as a titanium alkoxide as a starting material. The titania monolith is manufactured by subjecting a titanium precursor, which is its starting material, to hydrolysis⋅polycondensation with water in parallel, and the titania monolithic gel is prepared through the sol-gel transition. However, methods for producing the titania monolith are limited because a titanium alkoxide [chemical formula: Ti(OR)4, wherein R is an alkyl group] has extremely high reactivity with a water molecule as compared to a silica gel manufactured by using a silica alkoxide as a starting material.
As a specific method for producing a titania monolithic porous body, the following Patent Document 1 discloses a method for producing a titania monolith by subjecting a titanium alkoxide to a reaction in an acidic aqueous solution having a pH of equal to or lower than 3.5 (the first conventional production method). In the first conventional production method, a titanium alkoxide is stabilized as a titanium chloride under strong hydrochloric acid before being proceeded to a sol-gel reaction. However, in the production method which uses a strong acid, a reaction is vigorous, and a production condition is restrictive. In addition, there is a problem that the method is not suitable for treatment of materials which does not have acid resistance such as coating onto a metal.
As a solution thereto, a method for synthesizing a titania monolith by hydrolyzing a titanium alkoxide under a mild condition which uses an organic solvent (the second conventional production method) is proposed in the following Non-Patent Documents 1 and 2. In the second conventional production method, a titania monolithic gel is manufactured by making hydrolysis⋅polycondensation reactions progress mildly due to the reaction of a stabilized titanium precursor, which is a titanium alkoxide to which an anion coordinates, with a water molecule.